24th IAEA Fusion Energy Conference - IAEA CN-197
Contribution ID : 645
Type : Poster
TH/P3-34: Development of a Predictive Capability for
Fast Ion Behaviour in MAST
Wednesday, 10 October 2012 08:30 (4:00)
Abstract content
A recent focus of the programme at MAST has been upon the development of tools to interpret and
understand the fast ion driven instabilities observed with a view to developing a predictive capability
for the future: In particular, which modes will be unstable, how will they behave, and what will be
the consequences? The drive arises from gradients in the fast ion distribution, and the calculation
of smooth high resolution 6D distributions (recently made possible using a GPU-based approach)
has allowed much more realistic simulations of the wave-particle interaction taking place. For the
resonant neutral beam ions in MAST, dynamical friction dominates over pitch-angle scattering and
facilitates a complex nonlinear wave evolution through the formation of structures in the fast ion
distribution. Dynamical friction has been captured within the HAGIS code by treating the collisional
terms as a combination of drag and a phase-space dependent Krook-like relaxation rate. Since
fusion-born alpha-particles are also slowing down in nature, this physics is expected to be important
in describing the behaviour of alpha-driven modes in future burning plasmas. Two new fast ion
diagnostics have been installed and commissioned on MAST: A 4-chord scanning neutron camera
and a FIDA system with toroidal and vertical views. Experiments have quantified the changes in the
fast ion distribution associated with the presence of internal n = 1 chirping modes. Simulations of
the coherent redistribution due to these modes has been described by diffusive and convective terms.
Subsequent simulations using only these transport coefficients reproduce the modifications to the
fast ion profile arising from the full wave-particle simulations motivating their adoption within more
global transport codes. As a further aid to experimental interpretation, synthetic forms of the MAST
neutron camera and FIDA views have been developed allowing a direct comparison between the
measurements and simulations, and providing confidence that the processes responsible for the fast
ion redistribution are correctly understood. This work was funded by the RCUK Energy Programme
under grant EP/I501045 and the European Communities under the contract of Association between
EURATOM and CCFE. The views and opinions expressed herein do not necessarily reflect those of
the European Commission.
Country or International Organization of Primary Author
United Kingdom
Collaboration (if applicable, e.g., International Tokamak Physics Activities)
Primary author(s) :
Dr. PINCHES, Simon (ITER Organization)
Prof. BREIZMAN, Boris (The University of Texas at Austin); Dr. CECCONELLO,
Marco (Uppsala University Sweden); Mr. LAKE, Richard (University of Warwick); Dr. LILLEY,
Matthew (Imperial College, London); Dr. MICHAEL, Clive (CCFE); Dr. SHARAPOV, SERGEI
(CCFE); Dr. AKERS, Rob (CCFE)
Co-author(s) :
Presenter(s) :
Mr. PINCHES, Simon (UK)
Session Classification : Poster: P3
Track Classification : THS - Magnetic Confinement Theory and Modelling: Stability